Bukkit

1.16
Remove redundant purging of old files on startup.
Fix maxPlayers property on instance portals.
Fix maxInstances property on instance portals.
Fix recreateTime property on instance portals.
Fix unloadTime property on instance portals.
Fix inconsequential exception in the file purge task.
1.15
Fixed long standing issues with Windows preventing deletion of files.
Fixed long standing issues with Minecraft caching files from worlds which are not loaded.
Added the 'environment' property to portals, end and nether based instances will work now.
Removed scoreshare support.
1.14
Fix command block editing.
Add support for command minecart editing.
1.13
Add support for 1.7.8
Add support for 1.7.5
1.12
Add support for 1.7.2
1.10
Add support for 1.5.2
Add support for 1.6.1
Add support for 1.6.2
Add support for 1.6.4
1.9
Fix broken builtin packet handling.
Fix broken ProtocolLib packet handling.
Add WorldGuard support.
Add scoreboard support for parties via ScoreShare plugin.
Fix bugs relating to mob spawners which can spawn multiple entities.
1.8
Use ProtocolLib if present for modifying packets related to editing command blocks as non operator.
Modify built in packet modifying support to be more friendly to other plugins who hook into the same part of net.minecraft.server
Support for CraftBukkit 1.5.1
Fix instance deletion on Windows.
Added maximum party size per instance.
Added maximum number of instances per instance portal.
1.7
Added Support for CraftBukkit 1.5
Disabled portals for players in a vehicle.
Rewrote dependency handling code.
Removed support for economies via Multiverse-Core.
Improved Multiverse-Core support, instances now have all of their parent world's settings.
Preserve the direction a player is facing when they use a portal.
Add option to set the direction a player is facing when they use a portal.
Added economy support via Vault.
Added a default party setting for portals, which players not in a party will be added to.
Instances for players in the default party should always be numbered 0, for other parties they are numbered started at 1.
Print console warnings for people using instances from loaded source worlds, and force save them before loading an instance.
1.6
Lazily create interfaces for soft dependencies since they may not yet be enabled.
Fix issues with villages.dat and idcounts.dat not being separate for instance worlds.
Fix World.getWorldFolder() throwing ClassCastException for instance worlds.
Do not cache chunks from instanced worlds in memory.
Do not keep spawn in memory for instanced worlds.
1.5
Add support for using WorldEdit's selection tool for portal creation.
Declare soft dependencies correctly in plugin.yml
Cleanup soft dependency code so it's much less likely to break plugin startup.
Added a lot of logging to soft dependency loading.
Fix issues with overlapping portals.
1.4
/icmd now just places a command block in your hands.
/icmd related permissions are now applied when users edit the command block by right clicking.
Custom packet handling to allow editing command blocks without OP.
1.3
Fixed a bug where instances where not removed from a party when they are deleted, causing an exception when subsequently they were deleted again.
Added /ispawner create command to turn an Entity into a spawner.
Improved /ispawner command to instantly update the spawner rather than having to wait for it to spawn a monster.
Improved TileEntity writing code to cause the client to update immediately.
Fixed a bug where the plugin detected Multiverse-Inventories as present when it is not.
1.2
Fix bug where homes and spawn setting were sometimes lost on a server restart.
Added /icmd command for creating and editing command blocks, with ability to restrict command usage with permissions.
Cleaned up code for reading & writing TileEntity NBT data.
1.1
Allow setting the spawn world to none, to avoid conflicts with other plugins. Note: if a player is in an instance which gets deleted, they will be teleported to the first world's spawn point if there is no spawn world set.
Added support for setting gamemode, based on a third party worldmanager's gamemode setting for the world. Multiverse is the only supported world manager.
Rewrote instance loading code, no longer requires destination world to be loaded.
Instances no longer always spawn monsters, this setting should be correctly cloned from the destination world.
Instances have their own chunk generator which only generates empty chunks.
Fixed bug with instance unloading happening whilst players are in the instance.
Fixed bug with instance unloading never happening in some cases.
Instance difficulty is now a setting on the portalpair, defaults to difficulty of the destination world at creation time.
Optimized onPlayerMove to only perform checks when the player has crossed a block boundary.

Creating horse spawners will crash any client which tries to render it (client bug).
To spawn horses you need to use "entityhorse" rather than "horse" with the imob and ispawner commands.
Only limited testing has been performed.
Backwards compatibility is maintained.